title: Substrate specificity of age-related changes in the inducibility of hepatic microsomal monooxygenases in middle-aged rats.
abstract: Hepatic microsomal monooxygenase induction was investigated in young-adult and middle-aged male Fischer 344 rats. Monooxygenase components and drug metabolism activities were determined in liver microsomes prepared from rats treated with phenobarbital (PB, beta-naphthoflavone (BNF) or methyltestosterone (MT) and compared with values from untreated rats. PB and BNF effects on cytochrome P-450 concentration and cytochrome c reductase activity were similar in young-adult and middle-aged animals. However, the extent of cytochrome P-450 induction by MT was less in the older animals. The age-related changes in induction of drug metabolism activities differed with different substrates for the monooxygenase system. In contrast to the inducibility of benzphetamine N-demethylation and aniline hydroxylation, which was diminished in the older rats, the inducibility of nitroanisole O-demethylation was enhanced. The results imply that qualitative changes in the microsomal enzyme system occurred as the animals progress from young to middle adulthood.
mesh_terms: D000375:Aging; D000815:Aniline Hydroxylase / Q000096:biosynthesis; D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D004790:Enzyme Induction / Q000187:drug effects; D008297:Male; D008777:Methyltestosterone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000096:biosynthesis*; D009251:NADPH-Ferrihemoprotein Reductase / Q000096:biosynthesis; D009575:Nitroanisole O-Demethylase / Q000096:biosynthesis; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D019324:beta-Naphthoflavone
chemical_list: D001571:Benzoflavones; D019324:beta-Naphthoflavone; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D009575:Nitroanisole O-Demethylase; D000815:Aniline Hydroxylase; C019781:benzphetamine N-demethylase; D010089:Oxidoreductases, N-Demethylating; D009251:NADPH-Ferrihemoprotein Reductase; D008777:Methyltestosterone; D010634:Phenobarbital